Japanese provide new options in gas engines
As a pointer to Kawasaki Heavy Industries’ plans to make its Green Gas Engine series available to the marine market, two 12-cylinder versions of the spark-ignited, medium-speed design have been written into the specification for K Line’s conceptual, LNG-fuelled car carrier.
David Tinsley writes: KHI implemented its Green Gas Engine programme on the strength of soaring demand for energy efficient, environmentally compatible solutions in the power generation industry. Product performance has been improved this year through the release of new models of the 12- and 18-cylinder vee-form engines offering what is claimed to be a record 49% electrical efficiency at the generator terminal.
Development work is in hand to extend the market reach of the KG engine series to ship power applications, thereby promising an additional gas engine sourcing option for marine buyers. In the meantime, a ‘taster’ as to the scope of the brand has been provided by the futuristic K Line ro-ro vehicle carrier. This is foreseen with two KG-12 gas engines rated at 5,000kW each and turning a single, controllable pitch propeller through a twin-input/single-output gearbox. The gearbox has a PTO (power take-off) generator drive for each engine.
The proposed ship design, which departs from conventional exterior lines through its domed, forward superstructure and rounded foreship section, has a capacity of 2,000CEU (car-equivalent units). As the vessel type is slanted at north European operations, progress in the development of the European bunkering infrastructure will have a signal bearing on the project and its timescale. According to K Line, the use of LNG fuel, rather than conventional bunker oil, will cut CO2 by 40%, NOx by 80-90%, and virtually eliminate SOx and particulates.
The Kawasaki KG engines employ a pre-chamber where a spark-ignited gas flame is generated, with the air-fuel mixture combusted in the main chamber. The lean-burn technology in conjunction with a pre-chamber design and spark plug ignition obviates the need to use a liquid fuel for pilot ignition, as in dual-fuel engines.
The KG-12 and KG-18 engines produce, respectively, 5,200kW and 7,800kW in 50Hz/750rpm versions, and 5,000kW and 7,500kW as 60Hz/720rpm aggregates. Power generation efficiency for both models is given as 48.5%, with NOx emissions of less than 0.8kg/kWh.
In March 2011, the company announced an extension to its Green Gas Engine portfolio through the development of the KG-12-V and KG-18-V series, wherein the V signifies ‘variable nozzle system’. By realising a 0.5% efficiency improvement over the standard KG-12 and KG-18 types, the KG-V versions are claimed to set a new world record in fuel-to-electricity efficiency rate.
The key to the performance enhancement in the latest engines is the adoption of variable turbine nozzle area turbocharger technology, making more effective use of exhaust energy. Power outputs in both the 50Hz and 60Hz generator configurations are unchanged from the KG series.
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